Process for the production of electric conductor material from copper having high conductivity



United States Patent PROCESS FOR THE PRODUCTION OF ELECTRIC CONDUCTOR MATERIAL FROM COPPER HAV- ING HIGH CONDUCTIVITY Carl Hermann Weeber, Schladern, and Herman Schunck, Bonn (Rhine), Germany, assignors to Elmores Metall-Aktiengesellschaft, Schladern, Germany No Drawing. Filed Aug. 11, 1958, Ser. No. 754,167

Claims priority, application Germany Aug. 12, 1957 2 Claims. (Cl. 204-9) The present invention has for its object to develop a simple process, by the application of which electrical conductors, such as wires, tubes, bus bars, coils for transformers and the like can be produced with higher conductivity than has heretofore been possible.

*It is well known to subject crude copper, which generally contains 94-97% of copper, to a fine purification by fire refining or by electrolytic refining. The cathode plates produced by the latter method contain more than 99% of pure copper, but they must first be remelted before being further used, whereafter the copper is pressed, drawn or rolled into the appropriate normal commercial forms, such as billets, sheets, wires and the like. For electrotechnical purposes, therefore, electrolytic copper has heretofore first been melted and thereafter further worked up. It is known to the person skilled in the art that the conductivity of this electrolytic copper refined and remelted in the usual way does not exceed 5 8 Siemens units. t

For separating a particularly compact, pure copper from the electrolytic bath, a method is known in which the surface of the rotating tubular cathode is worked by a smooth, hard tool, for example an agate stone, which is passed over the said cathode during the separation. This so-called Elmore method gives large-calibre copper tubes having the desired wall thickness. In some cases, the tubes or vessels thus produced, which may be profiled, or the plates cut from the tubes, may be directly employed for the construction of apparatus. On the other hand, this copper, which is compacted in the electrolytic deposition, has not been further worked up into electric conductors by reason of its high cost as compared with that of normal electrolytic copper. It has now been found that copper conductor material having a conductivity of more than 60 Siemens units can surprisingly be obtained if the copper obtained by the Elmore process and mechanically worked up during the deposition (for example smoothed and compacted by glass balls) is not remelted, but is only subjected to a mechanical treatment, such as drawing, pressing or rolling, in order to produce the desired form. The full annealing which may be necessary between the individual working stages is preferably carried out in an inert or oxygen-free atmosphere in order to prevent absorption of oxygen or like gases, which would adversely affect the conductivity.

Accordingly, it is an object of this invention to provide a process for the production of copper of very high conductivity.

It is advantageous so to effect the electrolytic deposition that the metal is obtained in a form suitable for the proposed use. Thin copper tubes for coils through which a cooling agent is passed, for example, can be produced from the obtained tubes by drawing. For the production of wire or wire coils, the tubes may be cut spirally and the copper strip thus obtained may be drawn to the desired wire thickness. Alternatively, an endless strip or an endless wire may be produced by turning on a lathe from the copper tubes produced by the Elmore method, the said strip or wire thereafter being further worked up in the usual manner.

The working-up according to the invention (obtained by the Elmore method or a similar method) has proved particularly advantageous for the production of high current windings, such as secondary coils in heavy-current transformers. In such cases, the electrolytically obtained tubes are cut spirally, so that a coil is obtained, the dimensions of which may correspond to the original tube. A further advantage is that an optimum utilization of the coil space can be obtained by reason of the rectangular cross-section of the turns. The inner and outer surfaces of the winding are smooth, so that the arrangement of the primary coils is facilitated.

For the production of blocks, it is particularly advantageous to produce, instead of a hollow cylinder as heretofore in the electrolytic deposition, a solid block which may thereafter be brought to the desired thickness in a manner known per se in an extrusion press or by a rolling operation. In order to achieve this, in accordance with the invention, a hollow cylinder of sufficient wall thickness is first produced in the usual manner (for example, as in the Elmore method, from which hollow cylinder a solid core can be milled or cut for the subsequent electrolysing process. Since the speed at which the copper is deposited in the electrolytic bath naturally depends upon the size of the surface of the cathode, the thickness of the initial cylinder will be made correspondingly large in order that a core of sufiicient diameter may be obtained. The wall thickness of the tube primarily produced should therefore amount to -200 mm. There is then cut from the said tube a segment which is thereafter converted into a round rod in known manner, for example on a lathe. The solid rod thus obtained, having a diameter of about 100-200 mm., is then employed as a core, i.e. as the cathode inthe Elmore electrolysing process. Its diameter will be increased inaccordance with the desired purpose of use by the application of copper with mechanical compaction. On completion of the electrolysis, the solid rod obtained, consisting of pure, compacted copper is subdivided. One of the sections obtained will be tapered by extrusion pressing or by a suitable rolling operation in order that it may thereafter be employed as a solid core for a copper coating operation, while the other sections are worked up as copper blocks for the production of wires and the like.

With this method of carrying out the process according to the invention, it is possible to produce round blocks from pure Elmore copper without remelting and without any chip-removing working stages. The first solid cathode rod is thus here obtained in the usual manner from a cylinder, While the cores subsequently required are merely prepared by extrusion pressing or rolling from the solid block material resulting from the preceding deposition.

In the following, the process according to the invention for the production of copper blocks will be more fully explained with reference to an example.

A segment is cut from a hollow cylinder produced in the usual manner by the Elmore method and having an internal diameter of 600 mm., an external diameter of 840 mm., and a length of 4 m., and a solid rod having a diameter of mm. is formed therefrom on a lathe. The rod thus obtained is then disposed in the electrolytic apparatus as a rotating cathode and copper is applied thereto with continuous smoothing of the surface until its diameter corresponds to the extrusion press receptacle, which generally has a width of 200 mm. The round solid copper block thus obtained is subdivided into lengths of 600 mm., which are usual for extrusion pressing. One

of the blocks thus obtained is brought to a diameter of 140 mm. in the extrusion press, whereby a round, solid rod having a length of 1220 mm. is obtained, which can thereafter be re-used as a cathode core in the application of copper by the Elmore method. The solid rod thus obtained is then again subdivided and a section is tapered by working in the extrusion press, whereatter it can again be employed as a core for the next electrolysing operation, while the remainder is employed for the desired purpose in the form of blocks.

' The new process is quite generally applicable to the manufacture of electric conductor material in all cases where conductor material can be directly produced from the electrolytic copper obtained with mechanical surface treatment and where high conductivity values are re- 'quired.

The electric conductors produced by the process according to the invention have considerable technical importance because it is thus possible for the first time to fully utilise the conductivity of pure copper in practice. The view has been held for decades that the conductivity :of copper could not be increased above 58 Siemens units for technical purposes. It is therefore very surprising that it is possible, by the simple method according to the invention, to produce conductor material which exceeds this value regarded as optimum by more than 2 units. By the application of the new process, it is possible to obtain electric conductors, the conductivity of which approaches that of silver, which is about 62 Siemens units, whereby a considerable saving of material can be achieved in the case of electric conductor material, to gether with a simplification in manufacture. By employing the highly conductive conductor material obtained in accordance with the invention, therefore, the wire cross-section may be reduced by up to 5% with the same current loading, whereby considerable reductions in weight, for example in the case of transformers, can be efiected because the weight of the iron parts can also be reduced. Since no remelting operation is carried out in the production of the electric conductor material, the dangers of contamination, for example by incorporation of oxygen or material from the melting crucibles, which are involved in such an operation are absolutely obviated. In the technical performance of the melting copper such impurities can never be entirely avoided and small traces of other substances are sufficient to produce a marked deterioration in conductivity.

While a specific example of the invention has been described in detail to illustrate the applicationof the invention principles, it will be understood that the invention maybe embodied otherwise without departing from such principles.

What is claimed is:

1. A process for the production of electric conductor elements having a conductivity of more than Siemens units which comprises forming a thick-walled tube of compacted electrolytic copper by electrolytically depositing and compacting said copper on a cathode, cutting segments from said thick-walled tube, forming first solid rods from said segments, further electrolytically depositing and compacting copper on said first solid rods to form second solid rods of greater diameter, mechanically fabrieating a portion of the said second solid rods into electrical conductor elements without melting said copper and reusing another portion of said second solid rods as a base for again electrolytically depositing and compacting said copper.

2. A process according to claim 1 including the step of annealing said compacted copper during the individual working stages in an inert atmosphere.

References Cited in the file of this patent UNITED STATES PATENTS 480,186 Elmore Aug. 2, 1892 485,919 Elmore Nov. 8, 1892 1,834,203 Cain et a1. Dec. 1, 1931 1,952,762 Levy et a1 Mar. 27, 1934 1,965,399 Wehe July 3, 1934 FOREIGN PATENTS 24,017 Great Britain of 1893 

1. A PROCESS FOR THE PRODUCTION OF ELECTRIC CONDUCTOR ELEMENTS HAVING A CONDUCTIVITY OF MORE THAN 60 SIEMENS UNITS WHICH COMPRISES FORMING A THICK-WALLED TUBE OF COMPACTED ELECTROLYTIC COPPER BY ELECTROLYTICALLY DEPOSITING AND COMPACTING SAID COPPER ON A CATHODE, CUTTING SEGMENTS FROM SAID THICK-WALLED TUBE, FORMING FIRST SOLID RODS FROM SAID SEGMENTS, FURTHER ELECTROLYTICALLY DEPOSITING AND COMPACTING COPPER ON SAID FIRST SOLID RODS TO FORM SECOND SOLID RODS OF GREATER DIAMETER, MECHANICALLY FABRICATING A PORTION OF SAID SECOND SOLID RODS INTO ELECTRICAL CONDUCTOR ELEMENTS WITHOUT MELTING SAID COPPER AND REUSING ANOTHER PORTION OF SAID SECOND SOLID RODS AS A BASE FOR AGAIN ELECTROLYTICALLY DEPOSITING AND COMPACTING SAID COPPER. 